1. Field of Invention
This invention relates to an industrial mulching apparatus for use in mulching vegetation such as brush, trees, etc., or stump grinding. In particular, this invention relates to improvements to a mulching unit including a plurality of cutting assemblies that serially engage and mulch the intended vegetation in rapid fashion.
2. Description of Related Art
FIGS. 1-4C show a related art mulching apparatus 10. The mulching apparatus 10 includes a tractor 12 supported on a set of wheels 14. The tractor driver can sit within a protected cage 16 positioned on a frame of the mulching apparatus 10. A hydraulic unit 18 connected to the tractor 12 provides a means by which a mulching unit 20 is positioned, e.g., laterally shifted, raised and lowered. The tractor 12 is commercially available from Barco, a manufacturer of tractors. Also, many details of the mulching apparatus 10 shown in FIG. 1 are described in U.S. Pat. No. 5,813,792 herein incorporated by reference in its entirety.
The tractor 12 is provided with one or more power sources, e.g., motors, sufficient to drive the tractor at a desired speed and to rotate the mulching unit 20 in the direction of arrow A. The mulching unit 20 can rotate at a speed of about 1,700 rpm, for example. The mulching unit 20 includes a plurality of cutting hammers 26 that are axially spaced along the length of the mulching unit 20. A plurality of spacers 27 are provided between each of the cutting hammers 26. The spacers 27 define sector shaped portions in which each of the hammers 26 pivots over a limited range. Movement within the sector shaped portion is in addition to the overall rotation of the mulching unit 20 in the direction of arrow A shown in FIG. 1. Centrifugal force causes each of the cutting hammers 26 to pivot radially beyond the limits of each spacer 27 to thereby engage brush, trees or other vegetation.
FIG. 2 is an enlarged view of the mulching unit 20. The cutting hammers 26 alternate with the spacers 27, and the hammers 26 pivot within each sector shaped portion defined by the spacers 27. The hammers 26 in one row are staggered with respect to the hammers 26 in adjacent rows to obtain a substantially continuous cutting profile.
FIG. 3 schematically shows the mulching unit 20 to include a pair of end plates 22 and a plurality of support rods 24. Each support rod 24 includes a plurality of cutting hammers 26. For example, each support rod 24 holds 10 to 12 cutting hammers 26. The cutting hammers 26 are freely rotatable about the support rods 24, and are sometimes referred to as "flail" mulchers or mowers.
FIG. 4A shows an enlarged view of the cutting hammer 26. In FIG. 4A, the cutting hammer 26 includes a through hole 28 defining an inner support surface that is slidably and rotatably mounted on one of the support rods 24 shown in FIG. 3. The through hole 28 is partly defined by a collar 30 on which a cutting clement 32 is formed. In operation, a distal end portion of the cutting element 32 wears away or erodes due to repetitive high speed impact with vegetation, the ground, etc. As such, it is necessary to replace the cutting element 32, which also requires replacement of the collar 30 since it is formed in one piece with the cutting element 32. Generally, this is done by disassembling one or both of the end plates 22 from the support rods 24, as shown in FIG. 3, and then sliding the collar 30 until the cutting hammer 26 disengages with the support rod 24. In this manner, one or more of the spent cutting hammers 26 can be replaced with new cutting hammers 26.
FIG. 4B shows another example of a related art cutting hammer 26' that is similar to the cutting hammer 26 shown in FIG. 4A. The main difference is that the cutting hammer 26' is double-ended and includes first and second cutting elements 32A and 32B. Thus, when one of the cutting elements 32A is spent, one or both of the end plates 22 (FIG. 3) can be detached from the support rods 24, and the cutting hammer 26' can be removed from the support rod 24 and reassembled in an opposite orientation such that the fresh or unspent cutting element 32A, rather than the spent cutting element 32B, engages with the intended vegetation. Otherwise, the cutting hammers 26 and 26' are identical in operation.
FIG. 4C is representative of a right side elevation view of either of the cutting hammers 26 or 26'. The cutting elements 32 and 32B (as well as the cutting element 32A) are generally flat and blade-like and are roughly equal in width to the width of the collars 30, 30'. This is disadvantageous because the flat and blade-like shape of the cutting elements 32 and 32B results in excessive frictional contact with the intended vegetation or the ground during the mulching operation. In particular, any dirt or other debris that comes in contact with the blade member must be directed completely around each cutting element 30 or 32', which causes undue strain on the motor or power source of the tractor 12.
Another disadvantage with the related art structure shown in FIG. 1 is that the mulching unit can become misaligned if the mulching unit impacts various obstacles during operation. For example, the assembly of the end plates 22 and support rods 24 may not sufficiently resist deformation when impacting obstacles during the mulching operation.
Another related art mulching apparatus includes a rotatable drum having bullet-like cutting elements fixedly attached to the outer surface of the drum. These cutting elements are made from tungsten or carbide and are commonly used in asphalt grinding machines. However, deformation of the drum unit is problematic because it has a relatively fragile structure not well suited to resisting impact.